The invention relates to a sensor arrangement for the detection of specimen containers.
Such specimen containers take the form, in particular, of test tubes that are filled with fluid, each being closed by means of a cap. Such test tubes typically contain medical specimens. One example is test tubes filled with blood specimens that are used for blood analysis. The test tubes are automatically allocated to various stations for analysis purposes.
In this connection, the individual test tubes must be detected and identified, especially in order to avoid mix-ups and incorrect allocations.
A code, especially a barcode, is usually applied to each test tube for the purpose of specimen identification.
One known method for detecting such test tubes in an automated system is the use of optical sensors, which typically have an image sensor, i.e. a camera, as a receiver. Such optical sensors must detect both the test tube itself, for example by using contour detection means, as well as the code on the test tube.
U.S. Pat. No. 8,170,322 B2 discloses such an optical sensor by means of which test tubes are detected against a retroreflective background. The highly reflective background results in the specimen test tube appearing as a dark object against this background. Although this arrangement also allows for the reading of codes on test tubes, object detection or object classification is only possible to a limited extent in this case. In particular, no color detection is possible.
Furthermore, it is disadvantageous with regard to such systems that different camera images must be used for object detection, on the one hand, and barcode detection, on the other hand, and these different images are recorded under different lighting conditions.
U.S. Pat. No. 8,170,271 B2 discloses another optical sensor with a camera for the detection of test tubes. In this system, a background having a dark region is used. The test tube is positioned such that the barcode on the test tube can be detected against this background. On the other hand, the test tube is positioned in front of a retroreflective background in order to detect the geometry of the test tube.
U.S. Pat. No. 8,248,590 B2 discloses a sensor arrangement with an optical sensor in which a flat, dark surface is provided to serve as a background, which is laterally limited by retroreflective areas running at an angle to it. Barcodes applied to a test tube can be detected against the dark background surface. The contour of the test tube can be detected by means of light rays emitted by the optical sensor which are conducted to the test tube via the retroreflective areas.